1. Field of the Invention
This disclosure relates to the field of dental instruments. In particular, to ultrasonic microtube dental instruments designed to remove the remnants of broken instruments from teeth.
2. Brief Description of the Related Art
During root canal preparation procedures, the potential for instrument breakage is always present. When an instrument breaks during the procedure, the clinician is generally left with two options, attempt to remove the broken instrument, or leave the broken instrument in place and bypass the broken instrument while continuing the procedure.
Historically, the consequences of leaving and/or bypassing broken instruments have been discussed in dental literature and can be serious. In some cases, leaving the broken instrument in the tooth can necessitate extraction of the tooth in the future resulting in a loss of any benefit obtained from performing the root canal procedure in the first place.
It is therefore generally preferred that the broken instrument be removed from the tooth to prevent additional problems down the road. Historically, retrieving broken instruments posed formidable challenges. In particular, most broken instruments were files, drills, bores, or other cutting instruments that broke because of becoming wedged inside the structure of the tooth. Therefore, the very fact that the instrument was broken generally indicated that the instrument had become stuck in the tooth structure and could not be easily pulled free. Further, the instrument would often break at a point not easily visible or accessible to the clinician as a drill or similar instrument could break at a point within its own hole and therefore can not be accessed by an instrument larger than it itself without boring out additional space.
Generally, to be able to carry out an instrument retrieval, a clinician needs to open space around at least a portion of the broken instrument. In this way, another instrument which can interact on the broken instrument can be brought into contact with the broken instrument so as to allow the broken instrument to be removed. For instance, a pulling device can be placed in contact with an end of the broken instrument to allow for the broken instrument to be pulled free. Alternatively, an instrument may be used that attempts to rotate the broken instrument backwards and essentially unscrew it from the obstruction it encountered. In still further situations, as structure is removed from around the broken instrument, the structure causing the wedge may be destroyed freeing the broken instrument.
Traditionally, small files were used in efforts to either bypass or eliminate the broken instrument. As time has passed and technologies improved, retrieval techniques have evolved but are still oftentimes ineffective because of limited vision and/or restricted space. Because of the need to access the instrument and visualize the correction, efforts directed toward instrument retrieval, even when successful, often weaken roots due to overzealous canal enlargement, which in turn predisposes them to subsequent fracture and the loss of a tooth. Indeed, the prognosis of a tooth is seriously compromised if the efforts to remove a broken instrument lead to iatrogenic events, such as a ledged canal or root perforation. In these situations, the tooth is again often lost and the purpose of the procedure was compromised by the broken instrument.
Because of these types of issues, the greatest challenge to removing broken instruments is to remove them safely without unnecessarily compromising the remaining tooth structure. A variety of different instruments, devices and resulting techniques have been advocated to remove broken instruments. Newer methods to remove broken instruments require drilling to expose the proximal (broken) end of the broken instrument and to allow instruments to access the proximal end. Various methods are utilized to bore around the proximal end to expose a few millimeters of the structure of a broken instrument. This end can then be acted upon by instruments for effectuating the removal by backing out or pulling the broken instrument free with a high degree of success. Methods for exposing the critical millimeters generally the include utilizing high and low speed rotary cutting burs, and manual and rotary trephines.
The problem with these methods for exposing the broken instrument is the size of the instruments and techniques employed oftentimes result in excessive loss of tooth structure during these procedures. In particular, because the instrument being used to expose the tip is generally no smaller than the broken instrument, the diameter of the removed material can be three times what it would have otherwise have been due to having to bore around the broken instrument. Further, if smaller instruments are used, there is risk that these instruments (which are much more fragile than the broken instrument was) may also break further complicating the problem. For these reasons, it is not uncommon for iatrogenic problems to occur when attempting to retrieve a broken instrument. Namely, overzealous radicular access can equate to a loss of root structure which contributes to root fracture. In other instances, deviating from the long axis of a canal while attempting to drill around can lead to a ledge or a root perforation.